ICE: assertion failed: !is_undef(val)

[nagisa]

code:

#![crate_type="rlib"]
fn test() -> (u8,) {
    (-1.0 as u8,)
}

output:

error: internal compiler error: unexpected panic
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports
note: run with `RUST_BACKTRACE=1` for a backtrace
thread 'rustc' panicked at 'assertion failed: !is_undef(val)', /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_trans/trans/adt.rs:1191

stack backtrace:
   1:     0x7efef723ab39 - sys::backtrace::write::hc94f8d9af2b8711fGUs
   2:     0x7efef72427c6 - panicking::on_panic::hc9accb046dad794bVhx
   3:     0x7efef72006f2 - rt::unwind::begin_unwind_inner::ha72df769ba895a835Ww
   4:     0x7efef690e37e - rt::unwind::begin_unwind::h5106877066291017917
   5:     0x7efef694fc91 - trans::adt::build_const_struct::hbb786125a90b0fb7Xmf
   6:     0x7efef694ef56 - trans::adt::trans_const::h6cc90ccc1716f7e53cf
   7:     0x7efef69d7af4 - trans::consts::const_expr_unadjusted::ha82c6847f10eb80czLs
   8:     0x7efef697fd02 - trans::consts::const_expr::ha03b4aa86aea5b9envs
   9:     0x7efef69d6a3a - trans::consts::get_const_expr_as_global::h64bc675b732942d1yss
  10:     0x7efef69ece6e - trans::expr::trans_into::hd1fc0e2f51949c52W6z
  11:     0x7efef697204e - trans::controlflow::trans_block::h3006d43e68f8b11dZ2u
  12:     0x7efef6970af1 - trans::base::trans_closure::h58b74be4b3f2d114KCh
  13:     0x7efef697262a - trans::base::trans_fn::h8b381b99cc95435dsNh
  14:     0x7efef69756c7 - trans::base::trans_item::h0f743e9af025fb97Ebi
  15:     0x7efef6983a1d - trans::base::trans_crate::hc043d7f7defe4b48E0i
  16:     0x7efef77abe0a - driver::phase_4_translate_to_llvm::h646ecc6a8cb7c383lOa
  17:     0x7efef77840ba - driver::compile_input::h3818778b4ba8e92bQba
  18:     0x7efef7844331 - run_compiler::h474493aa09b9a3f5D4b
  19:     0x7efef7841f82 - boxed::F.FnBox<A>::call_box::h16338820608853103440
  20:     0x7efef78414b9 - rt::unwind::try::try_fn::h1219638071771381846
  21:     0x7efef72b9fd8 - rust_try_inner
  22:     0x7efef72b9fc5 - rust_try
  23:     0x7efef7841768 - boxed::F.FnBox<A>::call_box::h2630035671385432388
  24:     0x7efef72416b1 - sys::thread::create::thread_start::h8a67470ee39a7f26cgw
  25:     0x7efef12f8373 - start_thread
  26:     0x7efef6e8927c - clone
  27:                0x0 - <unknown>

EDIT: minimized example a bit

[huonw]

cc #10184

[Mark-Simulacrum]

No longer ICEs, warning list below:

warning: function is never used: `test`
 --> <anon>:2:1
  |
2 |   fn test() -> (u8,) {
  |  _^ starting here...
3 | |     (-1.0 as u8,)
4 | | }
  | |_^ ...ending here
  |
  = note: #[warn(dead_code)] on by default

warning: can't cast this type
 --> <anon>:3:6
  |
3 |     (-1.0 as u8,)
  |      ^^^^^^^^^^
  |
  = note: #[warn(const_err)] on by default

warning: can't cast this type
 --> <anon>:3:6
  |
3 |     (-1.0 as u8,)
  |      ^^^^^^^^^^
  |
  = note: #[warn(const_err)] on by default

warning: can't cast this type
 --> <anon>:3:6
  |
3 |     (-1.0 as u8,)
  |      ^^^^^^^^^^
  |
  = note: #[warn(const_err)] on by default